Which QPST version are you using?
https://www.copy.com/s/dWIDcOMy3KBK/...ild%204.11.zip
4.11 version should do the trick. I guess you have read these thread's pages on XDA:
http://forum.xda-developers.com/show...597590&page=82
Sorry for being persistent, but I think you need a clean XP (or WIN7 32bit) installation... I encourage you to try. It is worth to try, or at least you can also remove all your qpst drivers and have a new attempt. I'm pretty sure that it is related to drivers and OS. I have found many ppl with the same problem, but couldnt help 'em much more than showing my own way to save it from fastboot loop mode.
Here is another one that rescued his device with XP. The best thing of doing the rescue procedure on XP is that there ain't problems with signed drivers and maybe there are some other advantages in terms of compatibility.
I also give you a link with a copy of the drivers I used to rescue my phone, here you are
https://www.mediafire.com/?hzbc2rhmgzn7qyq
04-09-2014 19-51-01.jpg
Use the ones in the above folder.
good luck